diff --git a/content/build/nsContentDLF.cpp b/content/build/nsContentDLF.cpp
index a29a0e20d80b..15641482361b 100644
--- a/content/build/nsContentDLF.cpp
+++ b/content/build/nsContentDLF.cpp
@@ -271,12 +271,13 @@ nsContentDLF::CreateInstanceForDocument(nsISupports* aContainer,
     rv = NS_NewDocumentViewer(getter_AddRefs(docv));
     if (NS_FAILED(rv))
       break;
-    docv->SetUAStyleSheet(gUAStyleSheet);
+
+    docv->SetUAStyleSheet(NS_STATIC_CAST(nsIStyleSheet*, gUAStyleSheet));
 
     // Bind the document to the Content Viewer
-    rv = docv->LoadStart(aDocument);
-    *aDocViewerResult = docv;
-    NS_IF_ADDREF(*aDocViewerResult);
+    nsIContentViewer* cv = NS_STATIC_CAST(nsIContentViewer*, docv.get());
+    rv = cv->LoadStart(aDocument);
+    NS_ADDREF(*aDocViewerResult = cv);
   } while (PR_FALSE);
 
   return rv;
diff --git a/content/build/nsContentDLF.h b/content/build/nsContentDLF.h
index a62048a6fb4f..82c8a31f8aab 100644
--- a/content/build/nsContentDLF.h
+++ b/content/build/nsContentDLF.h
@@ -20,6 +20,8 @@
 
 #include "nsIDocumentLoaderFactory.h"
 #include "nsIDocStreamLoaderFactory.h"
+#include "nsIDocumentViewer.h"
+#include "nsIDocument.h"
 
 class nsICSSStyleSheet;
 class nsIChannel;
diff --git a/layout/build/nsContentDLF.cpp b/layout/build/nsContentDLF.cpp
index a29a0e20d80b..15641482361b 100644
--- a/layout/build/nsContentDLF.cpp
+++ b/layout/build/nsContentDLF.cpp
@@ -271,12 +271,13 @@ nsContentDLF::CreateInstanceForDocument(nsISupports* aContainer,
     rv = NS_NewDocumentViewer(getter_AddRefs(docv));
     if (NS_FAILED(rv))
       break;
-    docv->SetUAStyleSheet(gUAStyleSheet);
+
+    docv->SetUAStyleSheet(NS_STATIC_CAST(nsIStyleSheet*, gUAStyleSheet));
 
     // Bind the document to the Content Viewer
-    rv = docv->LoadStart(aDocument);
-    *aDocViewerResult = docv;
-    NS_IF_ADDREF(*aDocViewerResult);
+    nsIContentViewer* cv = NS_STATIC_CAST(nsIContentViewer*, docv.get());
+    rv = cv->LoadStart(aDocument);
+    NS_ADDREF(*aDocViewerResult = cv);
   } while (PR_FALSE);
 
   return rv;
diff --git a/layout/build/nsContentDLF.h b/layout/build/nsContentDLF.h
index a62048a6fb4f..82c8a31f8aab 100644
--- a/layout/build/nsContentDLF.h
+++ b/layout/build/nsContentDLF.h
@@ -20,6 +20,8 @@
 
 #include "nsIDocumentLoaderFactory.h"
 #include "nsIDocStreamLoaderFactory.h"
+#include "nsIDocumentViewer.h"
+#include "nsIDocument.h"
 
 class nsICSSStyleSheet;
 class nsIChannel;